Explicit dependencies using require

Please consider to refactor the package code in favor of explicit dependencies (instead of `//=` preprocessor comments) using require to support webpack/browserify wrokflows. Also please explicitly require raphael and add it `package.json` `dependencies`. FYI raphael master branch [already supports browserify](https://github.com/DmitryBaranovskiy/raphael/commit/3236fa65d7efd9a894dd3134074b8503214c40df). IMHO this change will be very useful.